1. Field of the Invention
The present invention relates to tool inserts such as a cutting insert used in machining operations, blanks for forming such tool inserts and a method of manufacture.
2. Description of the Related Art
Machining methods such as turning or milling require the use of cutting tools made from hard materials. Cemented tungsten carbide was developed many decades ago as a much harder alternative to steel. Cemented tungsten carbide may be brazed to a steel shank but it is more commonly employed as an “insert” that is attached to tool holder by clamping or by engaging a screw with a hole in the insert. Such inserts have an appropriate thickness and are provided in a variety of different geometries. Some of the more common insert geometries are triangular, square and rhombic inserts.
More recently, polycrystalline cubic boron nitride (PCBN) and polycrystalline diamond (PCD) materials have been used with inserts to provide a harder and more wear resistant alternative. Typically, small sections of PCBN or PCD are cut with a laser or electrical discharge machining (EDM) process and the small sections of PCBN or PCD are then brazed into a corresponding pocket in a cemented tungsten carbide insert. FIGS. 1-3 illustrate prior art inserts 10, 12 and 14 having a carbide body 16, 18, 20 and an inlayed section 22, 24, 26 formed out of either PCBN or PCD that has been secured in a pocket formed in the carbide body. The inlayed sections of PCBN or PCD form one or more cutting edges 28 on the insert. FIG. 1A which provides a perspective view of insert 10 with its inlayed section 22 secured to carbide body 16.
The process of manufacturing an insert typically involves forming an insert blank that has the desired geometry but which is slightly larger than the desired final dimensions of the cutting insert. The insert blank is then ground, using a diamond grit wheel, to remove the excess material and form the cutting edge of the insert. While this does not present undue problems with insets having a PCBN cutting edge, the grinding time and grinding wheel consumption involved in grinding a PCD cutting edge presents a significant expense. An improved tool insert blank and manufacturing method that allows for the more cost-effective production of tool inserts is desirable.